1. Field
Embodiments relate to a compound for an organic optoelectronic device and an organic light emitting diode including the same.
2. Description of the Related Art
An organic optoelectronic device is a device using a charge exchange between an electrode and an organic material by using holes or electrons.
An organic optoelectronic device may be classified as follows in accordance with its driving principles. A first organic optoelectronic device is an electronic device driven as follows: excitons are generated in an organic material layer by photons from an external light source; the excitons are separated into electrons and holes; and the electrons and holes are transferred to different electrodes as a current source (voltage source).
A second organic optoelectronic device is an electronic device driven as follows: a voltage or a current is applied to at least two electrodes to inject holes and/or electrons into an organic material semiconductor positioned at an interface of the electrodes, and the device is driven by the injected electrons and holes.
Examples of an organic optoelectronic device include an organic photoelectric device, an organic light emitting diode, an organic solar cell, an organic photo conductor drum, an organic transistor, or the like, which use a hole injecting or transport material, an electron injecting or transport material, or a light emitting material.
For example, an organic light emitting diode (OLED) has recently drawn attention due to an increase in demand for flat panel displays. In general, organic light emission refers to conversion of electrical energy into photo-energy.
Such an organic light emitting diode converts electrical energy into light by applying current to an organic light emitting material. It has a structure in which a functional organic material layer is interposed between an anode and a cathode. The organic material layer may include a multi-layer including different materials, for example a hole injection layer, a hole transport layer, an emission layer, an electron transport layer, and an electron injection layer, in order to improve efficiency and stability of an organic optoelectronic device.
In such an organic light emitting diode, when a voltage is applied between an anode and a cathode, holes from the anode and electrons from the cathode are injected to an organic material layer and recombined to generate excitons having high energy. The generated excitons generate light having certain wavelengths while shifting to a ground state.
A phosphorescent light emitting material may be used for a light emitting material of an organic optoelectronic device in addition to the fluorescent light emitting material. Such a phosphorescent material emits lights by transporting the electrons from a ground state to an exited state, non-radiance transiting of a singlet exciton to a triplet exciton through intersystem crossing, and transiting a triplet exciton to a ground state to emit light.
As described above, in an organic light emitting diode, an organic material layer includes a light emitting material and a charge transport material, for example a hole injection material, a hole transport material, an electron transport material, an electron injection material, or the like.
The light emitting material is classified as blue, green, and red light emitting materials according to emitted colors, and yellow and orange light emitting materials to emit colors approaching natural colors.
When one material is used as a light emitting material, a maximum light emitting wavelength may be shifted to a long wavelength or color purity may decrease because of interactions between molecules, or device efficiency may decrease because of a light emitting quenching effect. Therefore, a host/dopant system may be included as a light emitting material in order to improve color purity and increase luminous efficiency and stability through energy transfer.
A material constituting an organic material layer, for example a hole injection material, a hole transport material, a light emitting material, an electron transport material, an electron injection material, and a light emitting material such as a host and/or a dopant, that is stable and has good efficiency may enhance performance of an organic light emitting diode.
A low molecular weight organic light emitting diode may be manufactured as a thin film in a vacuum deposition method, and may have good efficiency and life-span performance. A polymer organic light emitting diode may be manufactured in an inkjet or spin coating method, and may have an advantage of low initial cost and being large-sized.
Both low molecular weight organic light emitting and polymer organic light emitting diodes may have an advantage of self-light emitting, high speed response, wide viewing angle, ultra-thin form, high image quality, durability, large driving temperature range, or the like. They may have good visibility due to self-light emitting characteristics compared with a LCD (liquid crystal display), and may have an advantage of decreasing thickness and weight of LCD up to a third, because they do not need a backlight.
In addition, they have a response speed 1000 times faster in microsecond units than an LCD. Thus, they may realize a motion picture without after-image. Based on these advantages, they have been remarkably developed to have 80 times efficiency and more than 100 times life-span since they come out for the first time in the late 1980's. They keep being made larger, such as a 40-inch organic light emitting diode panel.